AQ131 refuses to get to plane speed

[BTrux]

Hello, I have a 87 Bayliner 2150 trophy hard top with the AQ131 and 270 outdrive running a 15.5 x 17 michigan ss prop. I have been fighting with it since I picked it up to get any kind of speed out of it. The best I have gotten is 11 mph testing on the lake today. I have rebuilt the carb twice, changed the timing belt and tensioner, checked the timing I don't know how many times now and put on a Holley electric fuel pump. It runs great till it's underload, then acts like I'm pulling a barge with it. Any help with its would be greatly appreciated.

 

[QBhoy]

Change the prop. I’m off the top of my head assuming that your too much prop there. That poor engine has a hard enough time trying to plane that boat, even perfectly propped. With a big diameter and stainless prop like that...it’s asking a lot of it really. Try going down a couple of inches in pitch and see.

 

[GA_Boater]

Welcome aboard.

Stop throwing parts at her. Do some diagnosis first.

Check for spark and compression on all cylinders for starters. How fresh is the gas? What is WOT RPM?

Probably weigh the boat, too. After 33 years, the foam can be soaked and adding more weight to push with 120 HP?

 

[BTrux]

Thanks guys, the parts I replaced needed to be done. The older guy I got it from left it set for a long time. It has fresh gas, good compression and spark. It has an ignitor electronic ignition. I was leaning more with your diagnosis QBhoy, but when I first got the boat it had an aluminum 14 x 13 on it and would only do 8 mph which is why I went bigger.

 

[kenny nunez]

Check how much the transom “flexes” when the drive is down and you stand on it. When the boat is idling observe the front of the engine then have someone put it in gear and try to plane the boat off, note how much the front of the engine rises .
The transom “flexes” like I think it is doing the drive is planting the bow down.
131 Volvos had no front engine mount, the higher HP model 151 had front mounts. You might luck out by adding a 151 front engine mount but the bottom line is you probably need a new transom.

 

[Stearns250]

I was having the same problem with my aq131a. It ended up being the coil. Is it hard to start after it warms up?

 

[Scott Danforth]

step 1, compression test
step 2, verify timing
step 3, verify the Anti Siphon valve is not stuck
step 4, weigh the boat. a 34 year old bayliner probably weighs 1000# more today than it did in 1987

 

[dennis461]

I'll list some simple things.
1. Is throttle plate opening all the way?
2. Does it have a dirty crushed flame arrester (on carb).
3. What is the out drive gear ratio.

Did the boat originally have a V-8 or 3.o liter V-6?

 

[kenny nunez]

Believe it or not but that engine combination was what that boat came with. When the boat was new and with 2 people plus 1/2 tank of fuel they did perform and could go between 30-35. The trick was that the back of the boat was lighter than the front which helped it plane off by not power dragging. I had a few that I worked on and at first could not believe what the customer’s told me. I did re power 1 with a V8 cobra package which did make a difference.
Needless to say they were known as a “entry level” boat.
There was a dealer that was selling them like hot dogs here in the New Orleans area, they never paid the floor plan and spent the $ as fast as they could until they were finally shut down. They would not even show the customers how to start and operate the boats.